I saw this specific issue after Windows updates had run on my cloud server. The Features & Roles sections within Server Manager were failing to display the relevant information, see below for the exact issue encountered:
When clicking on the Add Features or Add Roles buttons I would then see error HRESULT:0x800F0818:
Thankfully the resolution was very straight-forward – the first two hits from a Google search on HRESULT:0x800F0818 prescribed the correct fix. I used this link:
For me the issue was resolved by re-applying some files from the Windows6.1-KB947821-v14-x64.msu package. The Mircosft Update Readiness Tool will find the corrupt packages so you will know which packages to find and re-apply.